Method of making a compact fluid coupler for thermal inkjet print cartridge ink reservoir

Abstract

A method for joining two materials together to form a compact leak-resistant seal, particularly suited for use in thermal inkjet print cartridge ink reservoirs. The seal employs a shrink fit to clamp the two materials together. The method includes the steps of forming the first material into a desired first shot structure, placing the first shot structure in a second shot mold, and injecting the second material into the mold under adequate pressure and at an appropriate temperature. The second material has a high degree of mold shrinkage. Upon cooling, the second material shrinks tightly onto the first shot structure to form a molded joint which keeps air out and ink in when wetted and during normal shipping, storage, and operating conditions.

What is claimed is: 
     
       1. A method for forming a compact, leak-resistant joint between first and second moldable materials which define the frame of an ink-jetprint cartridge, the first material comprising a moldable rigid plastic and the second material comprising a moldable plastic characterized by a shrinkage rate as said second material cools, comprising a sequence of the following steps: molding said first material into a predetermined first shot reservoir frame structure defining at a snout end thereof an interior standpipe member through which a channel opening extends, said channel opening for carrying ink in a liquid state from an ink reservoir to a printhead region of said cartridge;   positioning said first shot structure in a second shot mold, said mold comprising first and second mold halves which can be closed about said first shot structure and define a portion of one or more mold cavities into which said second material is injected under pressure, and which can be opened upon cooling to permit removal of a molded structure therefrom, wherein a portion of said first shot structure also defines a portion of said one or more mold cavities, and wherein the second shot mold is provided with a channel mold pin for extending through said channel opening to prevent said second material from entering said channel during a second shot molding step, and with a cavity mold pin which extends across said channel opening, said channel mold pin stopping against said cavity mold pin;   injecting said second moldable material in a molten state into said mold as a second shot wherein said second material surrounds said standpipe member, said second material having a shrinkage rate as said material cools, and wherein said first shot structure comprises one or more shutoff surfaces against which said mold halves bear when closed about said first shot structure, and thereby shuts off a path for said molten second moldable material to flow when injected into said mold;   permitting said second material to cool, whereupon said second material shrinks about the periphery of said standpipe member, thereby forming a leak-resistant seal between said first and second materials about said standpipe, said seal resistant to leaks of said liquid ink out of said standpipe and resistant to air leaks through said seal into said reservoir.   
     
     
       2. The method of claim 1 wherein said first shot structure is characterized by one or more protruding peripheral ribs extending outwardly from said standpipe member, wherein said second material is molded about said one or more ribs. 
     
     
       3. The method of claim 1 wherein said first material is a modified polyphenylene oxide, and second material is a glass-filled polyethylene. 
     
     
       4. The method of claim 1 wherein said first material is polysulfone and said second material is glass-filled polyethylene.